The effect of planting date and plant density on phosphorus uptake and phosphorus harvest by Brussels sprouts

In experiments at Lelystad, Netherlands in 1989 and 1991/92, Brussels sprouts (cv. Kundry) were planted at 26 700, 33 400 plants/ha on 2 May, 30 May or 27 June in 1989 and 29 April, 28 May or 8 July in 1991. Plant density had no effect or only a limited effect on crop P concentration during the growing season, and had no effect on final crop P. A delay in planting reduced final P uptake, but increased P concentration in the crop and in the sprouts at harvest. Depending on planting date, 33-50 kg P was taken up by the crop by harvest. Of this, 40-60% was removed from the field in the sprouts. There were no interactions between the effects of planting date and plant density. It is suggested that the effect of planting date on P uptake has no consequences for P fertilizer recommendations. It is also suggested that current recommended P fertilizer rates are in excess of the amount of P harvested in the sprouts.